The great spread of vine growing has, over the years, made known to everyone how the quality of the grapes produced is affected by numerous factors, amongst which those with the greatest influence are certainly linked to the climatic and micro-climatic conditions in which the plant and the bunch develop.
However, while experience of climatic conditions, understood as an in-depth knowledge of the consequences linked to altitude, rainfall, humidity and other characteristic parameters of the regions in which the vine is grown, has generated numerous devices for treatment of the vine during its growth, less attention has been paid to the micro-climate, that is to say, what happens in the immediate vicinity of the bunch. In other words, no one ever thought to intervene in any way in the bunch growth process.
The natural evolution of bunch ripening is well known to experts and thoroughly described in numerous publications in the sector: first the buds form on the vine stem; when each bud opens a shoot emerges, on which there develop, at the nodes, first the leaves and then the rachises, which constitute the branched axes on which the grapes will develop, and from which the bunches of grapes take shape.
During the so-called floral structure step, on the rachis bunch-shaped inflorescences form which constitute the first stage of the bunch of grapes: after the flowering comes the so-called setting, during which the actual grapes form by transformation and swelling of the ovary of the flowers, then the grapes take on their definitive shape and the bunch acquires the features we all recognise. This is followed by harvesting, after which the leaves drop, close to winter.
Paying particular attention to the floral structure step, it may be seen that, while the naked rachis tended to develop upwards and, therefore, to take on a substantially vertical arrangement, from this moment and as the weight of the flowers (and subsequently the grapes) gradually increases, the rachis gradually bends downwards, until, when the bunch is ripe, the bending point is extremely close to the node from which the rachis originated. As is known, the sap which circulates in the plant tends to move upwards and its circulation is therefore hindered by the curvilinearity of the path it must follow to reach the end of the rachis during bunch ripening, that is to say, when due to the significant weight of the grapes, the rachis is bent downwards.
This difficulty in sap circulation may easily correspond firstly to a delay in bunch ripening and secondly to uneven ripening of the grapes, amongst which, in particular, those in the outer positions of the bunch may not fully ripen, because it is difficult for a suitable amount of sap to reach them.
Unevenness of the grapes makes it easier for parasites to attack the less healthy grapes, consequently penalizing the health of the entire bunch.
Finally, grapes in different conditions respond differently to treatments, making it practically impossible to identify operations which will benefit the entire bunch.